STIR boiling water into dry gelatin mix in medium bowl at least 2 minutes until completely dissolved. Stir in cold water.
POUR into 9-inch square pan. Refrigerate 4 hours or until firm.
CUT gelatin into 1/2-inch cubes. Layer gelatin cubes alternately with 1/2 cup of the whipped topping in 4 dessert glasses. Top with dollops of the remaining 1/2 cup whipped topping.